High capacity data networks rely on signal repeaters and sensitive receivers for low-error data transmission. To decode and/or cleanly retransmit a serial data signal, such network components include sub-components for creating a data timing signal having the same phase and frequency as the data signal. This step of creating a timing signal is known as “clock recovery.”
Data clock recovery requires a relatively high purity reference signal to serve as a starting point for matching the serial data signal clock rate and also circuitry for frequency adjustment. The type, cost and quality of the technology employed to generate the high purity reference signal varies according to the class of data network application. Typically, for remote or moveable systems, components including specially configured resonators have been used. As communication network technology progresses towards providing higher bandwidth interconnections to local area networks and computer workstations, the need has grown for smaller and cheaper clock recovery technology solutions.
For many higher frequency applications now in demand, resonator technologies such as surface-acoustic wave (SAW) resonators are sometimes used. These resonators are used in frequency translators for generating an output clock signal that is related to an input clock signal. Typically, the output clock signal is a fixed multiplied representation of the input clock signal. Moreover, the frequency translator maintains the output clock signal at a fixed phase relationship to the input or reference clock signal. Applications for frequency translators include, but are not limited to, providing a clock signal for synchronizing cellular telephone basestations to telecommunication network backbones.
The fabrication process used in producing frequency translators typically involves complex steps. Moreover, the steps in the fabrication process must be changed based on different requirements and operating parameters such as input and output clock signals. As a result of both the complex steps and different operating requirements, producing frequency translators with an adequate yield can be difficult.
One approach for improving yield is to produce a frequency translator that allows the user to choose the desired operating input and output clock signals of the translator. The user accomplishes this task by selecting from a plurality of configuration inputs connected to a microprocessor that controls the operation of the translator. However, using a microprocessor with the design of a frequency translator adds cost and increases the size of the device.
In addition to changing the general input and output characteristics of the frequency translator, an approach taken to optimizing the nominal frequency of the device is to frequency adjust the SAW resonator itself. However, this can be a difficult and costly task.
SAW based frequency translators are often sensitive to vibrations, a condition which has been labeled “microphonics.” Microphonics is a condition where the output frequency of the SAW resonator is modulated in an unwanted manner due to vibrations. Sources of external vibration can range from fans for cooling electronic circuitry, to road vibration caused by vehicle movement remote from the frequency translator.
Hence, there remains a need for a frequency translator design that is more cost efficient and vibration resistant.